152 Optimizing Head and Neck Cancer Radiotherapy using '5+5 mm’ DAHANCA Radiotherapy Guidelines

• Published in: Radiotherapy and oncology 2024-03, Vol.192, p.S38-S40
• Main Authors: Zukauskaite, Ruta, Kristensen, Morten H, Eriksen, Jesper G, Johansen, J⊘rgen, Sams⊘e, Eva, Johnsen, Lars, L⊘nkvist, Camilla K, Grau, Cai, Hansen, Christian R
• Format: Article
• Language: English
• Subjects: CTV; local control; radiotherapy guidelines
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/S0167-8140(24)00443-2

Primary radiotherapy treatment is preferred for squamous cell carcinomas in the head and neck region (HNSCC) owing to the preservation of anatomical structures and function. The delineation of treatment volumes, particularly the expansion from the gross tumour volume (GTV) to the high-dose clinical target volume (CTV1), is critical in radiotherapy planning. Historically, the choice of margin size for GTV-CTV1 has varied between different treatment centres in Denmark from zero to over 10 millimetres or could encompass the whole organ (volume) where the tumour is located. Therefore, the first DAHANCA IMRT guidelines could be referred to as volumetric-based. In 2013, national consensus guidelines were introduced by the Danish Head and Neck Cancer Group (DAHANCA), recommending an isotropic margin of five millimetres corrected only for air or natural anatomical barriers resulting in a more uniform geometrical margin. With over a decade of experience in applying geometrically-based GTV-CTV1 guidelines, the primary aim of this study was to assess whether the implementation of the guidelines in 2013 led to improved consistency in CTV1 volumes across different treatment centres. Additionally, we analysed whether changes in GTV-CTV1 margins moving from volumetric to geometric guidelines impacted 3-year local tumour control and local recurrence pattern in patients treated three years before and three years after implementation of the geometrical guidelines. The cohort consisted of 1,948 patients diagnosed with oro-/hypopharyngeal and laryngeal squamous cell carcinomas across three national treatment centres. The patients underwent definitive intensity-modulated radiotherapy (IMRT) in 2010-2012 when volumetric guidelines were used, and in 2013-2015, when geometric guidelines were adopted. The GTV-CTV1 margins were quantitatively assessed by calculating the median surface distance from the primary GTV to CTV1. Three-year local control (LC) rates were determined, and local recurrence patterns were examined (Figure 1) using a centre of mass (COM) analysis. Hazard ratios and corresponding 90% CIs were calculated using the Cox proportional hazard model to identify factors that influenced local tumour control. [Display omitted] The transition from volumetric to geometric guidelines substantially reduced median GTV-CTV1 margins, declining from a median of 9.0 mm (IQR 0.0-9.7) to 4.7 mm (IQR 4.0-5.5). Importantly, adopting geometric guidelines led to increased consistency in